Researchers from the University of Pittsburgh have created models that replicate the brain's complex electrical impulses in order to better understand neuron activity.

Many scientists are working to accomplish models that portray the billions of connections between neurons in the brain. For instance, researchers from the University College London have begun to map neural connections in mouse brains while University of Southern California researchers have invented a carbon nanotube synapse circuit that could bring them one step closer to building a synthetic brain.

Now, Henry Zeringue, study leader and a bioengineering professor in the University of Pittsburgh's Swanson School of Engineering, along with Ashwin Vishwanathan, Pitt bioengineering doctoral student, and Guo-Qiang Bi, neurobiology professor at Pitt's School of Medicine, have created models out of living brain cells in order to get a better idea of how neurons work behind memory formation.

Previous studies and magnetic resonance imaging (MRI) have shown that memories are formed when the outer layer of the brain, called the cortex, engages in extended electrical activity after "initial stimulus." But this is a difficult process to view in real time due to the complex nature of the brain's neural networks.

"We can look at neurons as individuals, but that doesn't reveal a lot," said Zeringue. "Neurons are more connected and interdependent than any other cell in the body. Just because we know how one neuron reacts to something, a whole network can react not only differently, but sometimes in the complete opposite manner predicted."

Now, Zeringue and the Pitt research team have created models that allowed them to witness this process in real time. They did this by stamping adhesive proteins onto silicon discs, and allowing the proteins to culture and dry. Then, cultured hippocampus cells taken from embryonic rats were fused to the proteins, allowing them to combine and grow into a natural network. The hippocampus is a part of the brain responsible for memory formation.

Researchers then worked to create and prolong the excited state that the cortex engages in after initial stimulus to view neuron activity. To do this, they disabled the cells' inhibitory response and used an electrical pulse to excite neurons.

The results were excited groups of 40 to 60 brain cells that were prolonged to 12 seconds in neuronal time. Normally, the observation of this process last .25 seconds in neuronal time. With this extended observation, researchers were able to see how neurons transmitted and held electrical charge, which is vital information for understanding the molecular and cellular basis of memory formation.